Zinc-plated steel sheet for hot stamping and production method therefor

Abstract

A zinc-plated steel sheet for hot stamping according to an aspect of the present invention includes a steel substrate and a plated layer provided on a surface of the steel substrate, in which the steel substrate contains, in % by mass, C: 0.10 to 0.5%, Si: 0.7 to 2.5%, Mn: 1.0 to 3%, and Al: 0.01 to 0.5%, with the balance being iron and inevitable impurities, and the steel substrate has, in the inside thereof, an internal oxide layer consists of an oxide containing at least one of Si and Mn having a thickness of 1 μm or more, and a decarburized layer having a thickness of 20 μm or less from an interface with the plated layer toward an internal direction of the steel substrate.

The invention claimed is: 
     
       1. A zinc-plated steel sheet for hot stamping, comprising:
 a steel substrate; and 
 a plated layer provided on a surface of the steel substrate, 
 wherein the steel substrate comprises, in % by mass relative to a total mass of the steel substrate:
 C: 0.10 to 0.5%, 
 Si: 0.7 to 2.5%, 
 Mn: 1.0 to 3%, and 
 Al: 0.01 to 0.5%, 
 
 wherein the steel substrate comprises an internal oxide layer and a decarburized layer, 
 wherein the internal oxide layer comprises an oxide of at least one selected from the group consisting of Si and Mn and has a thickness of at least 1 μm, 
 wherein the decarburized layer has a thickness of 20 μm or less from an interface with the plated layer toward an internal direction of the steel substrate, 
 wherein the internal oxide layer is a layer formed inside the steel substrate and near a steel substrate surface and the internal oxide layer does not appear on the steel substrate surface, 
 wherein an oxide film containing oxides of Si is not formed on the steel substrate surface. 
 
     
     
       2. The zinc-plated steel sheet of  claim 1 , wherein the steel substrate further comprises, in % by mass relative to the total mass of the steel substrate, 0.005% or less, excluding 0%, of B. 
     
     
       3. A method for producing the zinc-plated steel sheet of  claim 1 , the method comprising:
 holding a cold-rolled steel sheet at 500 to 720° C. for 120 to 400 seconds at a line speed of 45 to 200 mpm, in a reducing atmosphere with a dew point of −20 to 0° C., and 
 plating the cold-rolled steel sheet with a zinc-plated layer after the holding, 
 wherein the cold-rolled steel sheet comprises, in % by mass relative to a total mass of the cold-rolled steel sheet:
 C: 0.10 to 0.5%, 
 Si: 0.7 to 2.5%, 
 Mn: 1.0 to 3%, and 
 Al: 0.01 to 0.5%.